If you’re thinking of moving to a new network, and want to keep hold of the same iPhone, you may hit a snag: the device is locked to your current carrier and can’t be used with any other company.

A new iPhone 4S accessory claims to successfully SIM unlock all models of the AT&T Apple iPhone 4S running iOS 5.0 and 5.0.1 firmware. As AT&T, unlike rivals Sprint and Verizon Wireless, does not yet ...